TY - JOUR T1 - A Rapid in Vitro Screening for Delivery of Peptide-Derived Peptidase Inhibitors as Potential Drug Candidates via Epithelial Peptide Transporters JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 695 LP - 702 DO - 10.1124/jpet.104.066480 VL - 310 IS - 2 AU - Martin Foltz AU - Antje Meyer AU - Stephan Theis AU - Hans-Ulrich Demuth AU - Hannelore Daniel Y1 - 2004/08/01 UR - http://jpet.aspetjournals.org/content/310/2/695.abstract N2 - Targeting drugs or prodrugs to a specific enzyme by simultaneously targeting cell membrane carriers for efficient transport should provide the highest bioavailability along with specificity at the site of action. The peptide transporters PEPT1 and PEPT2 are expressed in a variety of tissues, including the brush-border membranes of epithelial cells of the small intestine and kidney. The transporters accept a wide range of substrates and are therefore good targets for a transporter-mediated drug delivery. Here, we report a screening procedure for peptidomimetic drug candidates combining two independent expression systems: 1) a competition assay in transgenic Pichia pastoris yeast cells expressing either mammalian PEPT1 or PEPT2 for identifying substrate interaction with the transporter binding site; and 2) a Xenopus laevis-based oocyte expression of the peptide transporter for assessing electrogenic transport of drug candidates. Based on the known oral availability and in vivo efficacy of the dipeptidyl peptidase IV (DPIV) inhibitor isoleucine-thiazolidide and its peptide-like structure, we first tested whether this compound is a substrate of epithelial peptide transporters. Additionally, a series of structurally related inhibitors were analyzed for transport. We identified various compounds that serve as substrates of the intestinal peptide transporter PEPT1. In contrast, none of these DPIV inhibitors showed electrogenic transport by PEPT2, although a variety of the compounds displayed good affinities for competition in peptide uptake in PEPT2-expressing cells, suggesting that they may serve as efficient inhibitors. In conclusion, we have applied an in vitro screening system that predicts efficient intestinal absorption of peptide-derived peptidase inhibitors via PEPT1 in vivo. The American Society for Pharmacology and Experimental Therapeutics ER -